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Dynaco Quadraphonic Simulator Circuit

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A hundred years ago when I assembled my first Dynaco pre-amp, amps, and tuner, there was a product developed by David Haffler (don't remember exactly what it was called) that used a very simple circuit that fed a stereo source to rear amps and speakers for a simulated "surround" effect. It worked quite well on some vintage recordings.

There was another version that allowed 4 speakers to be connected to a single stereo amp (I believe it summed cannels A+B and fed them to the rear speakers).

Does anyone have schematics to share?

Thanks.

Follow Ups:

RE: Dynaco Quadraphonic Simulator Circuit - teknofossil 18:46:14 03/23/11 (0)
Here is a schematic of the Quadradaptor.

-Tom
RE: Dynaco Quadraphonic Simulator Circuit - scarlett5689@att.net 19:14:31 02/26/11 (8)
Dynaco's QD-1 Quadadaptor connects two front and two rear speakers to one stereo amp. The manual is at http://www.akdatabase.com. Click on any of the mfrs shown, then click on 'Brands A-D'. Dynaco is on page 2, and the QD-1 is on page 2 of that - good pdf file. Depending on the setting of the attenuator control, the left rear speaker gets a mixture aL-bR, and the right rear gets aR-bL. Determining a and b is left as an exercise for the reader! (sorry, I'm too lazy just now). Note: The negative L and R amplifier input terminals are normally connected in the driving amplifier (as in the ST series for example).

There is a later version, the QD-1 II I think - may be a manual for that on the Internet, haven't looked.
- RE: Dynaco Quadraphonic Simulator Circuit - GP49 21:26:40 02/26/11 (7)
  "...The manual is at http://www.akdatabase.com. Click on any of the mfrs shown, then click on 'Brands A-D'. "
  
  Any of the mfrs shown EXCEPT Sansui!
  
  Don't ask how I know.
  
  GP49
  - RE: Dynaco Quadraphonic Simulator Circuit - ARnut 19:27:56 02/27/11 (6)
    Thanks for the tips. I was able to locate a manual and schematic. I am now thinking wiring a simple switching circuit that would be similar, but rather than driving four speakes from a single amp, would instead be inserted between the preamp and four separate power amps. Does that make sense? Any impedance or loading issues? Any suggestions?
    - RE: Dynaco Quadraphonic Simulator Circuit - teknofossil 19:20:00 03/23/11 (0)
      The link will bring you to a article detailing a tube based matrix which could be used to output basic surround channels which are similar to the basic Hafler (Dyna) quad. Left - Right (difference signal) for the rear channels and a Left + Right signal for a center channel. Not sure if you'd need additional input or output buffers. Early surround processors (Dolby surround) used something similar. Low pass filtering (above 8khz was rolled off @ 6dB/octave as I recall) and adjustable delay was added to the rear channels.
      
      -T
      Tube Cad Journal tube based L-R and L+R circuit (Open in New Window)
    - RE: Dynaco Quadraphonic Simulator Circuit - scarlett5689@att.net 10:31:15 02/28/11 (4)
      To do this at line level requires aome sort of phase inverter to derive the L-R and R-L signals. Take a look at sound.westhost.com, project #18, a good discussion showing a passive circuit using a transformer (expensive & hard to find) and an active circuit using op-amps. If you don't want center channel or sub-woofer outputs, you can leave that op-amp out. Might be nice to put a gain control at the rear output - 10K would be a reasonable value. Also, this circuit gives you L-R only, so to duplicate the effect of the 'Hafler circuit' shown in Fig 1, you could reverse the polarity of the right rear speaker. Not sure you'd hear much difference - try it!
      - IIRC - CharleyW 19:48:02 02/28/11 (3)
        
        In Reply to: RE: Dynaco Quadraphonic Simulator Circuit posted by scarlett5689@att.net on February 28, 2011 at 10:31:15
        
        there were two particular albums that sounded very ggod with DynaQuad - The Beatles "Let It Be" and the second "Blood, Sweat & Tears" ("And When I Die" in particular).
        
        RE: IIRC - GP49 21:23:51 02/28/11 (2)
        
        In Reply to: RE: IIRC posted by CharleyW on February 28, 2011 at 19:48:02
        
        Dynaco and Vanguard Records issued a demonstration LP with several selections from the Vanguard catalog that were particularly effective when played through a Dynaquad system. I still have mine.
        
        GP49
        
        RE: IIRC - ARnut 21:23:30 03/02/11 (1)
        
        In Reply to: RE: IIRC posted by GP49 on February 28, 2011 at 21:23:51
        
        Thanks for the posts. I looked at 'project 18' and it seems to be exactly what I am looking for. As I am not interested in center channel or subwoofer outputs, I guess I could simply disregard the second op-amp and its associated circuitry?
        Also, can it be battery powered? If so, would the -15 v. go to ground?
        
        RE: IIRC - scarlett5689@att.net 17:32:33 03/03/11 (0)
        
        In Reply to: RE: IIRC posted by ARnut on March 02, 2011 at 21:23:30
        
        In "project 18" Fig 3, you can omit parts R3, R4, R9, R10 VR1 and C1. With battery power, C2 and C3 need be only 100nF, connected close to socket pins 4 and 8.
        You can't omit U3B as it is part of the dual op-amp U3. Best way to disable it is to connect pin 6 to pin7, pin 5 to ground, pin 7 floating.
        Do NOT connect "-15V" to ground!! This really needs balanced + and - voltages - two 9 volt batteries should work well and give you a reasonable output. Total drain should be 7-10 mA, not too bad, but switch off both batteries when not in use!

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